JSFiddle - React, Tailwind, and code Playground
by WK_of_Angmar
JavaScript
var checkboxes = 20;
for (var j = 0; j <= checkboxes - 1; j++) {
var checkbox = document.createElement("input");
checkbox.setAttribute("type", "checkbox");
document.body.appendChild(checkbox);
}
var inputElements = document.querySelectorAll("input[type=checkbox]");
for (var i = 0; i <= inputElements.length - 1; i += 8) {
inputElements[i].checked = true;
inputElements[i+1].checked = true;
}